BIOLOGY 280 Study Guide - Final Guide: Background Extinction Rate, Shocked Quartz, Pioneer Species
16 Nov 2020
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Document Summary
The event of extinction caused there to be a continual turnover of species where every million years, an average of 25% of species go extinct (called the background extinction rate). In levels of extremes, when the level of extinction is much higher than the background extinction rate, then it"s considered a mass extinction. However, it turns out that not all individuals are equally subject to extinction. Based on the data of bivalves and gastropods (i. e. snails, clams good to fossilize), they compared the extinction rate of different species living in different sized geographical ranges. Patterns of the graph show that species living in a smaller geographic range are more likely to go extinct than species living in a bigger range. The end of the cretaceous mass extinction is the most recent, so it is easier to find a cause for it.
